Mycotoxin rainfall risk tool for cereals now covers the UK

We have switched on the mycotoxin rainfall risk tool for cereals for another season. Jason Pole explains how to use the tool, which now covers Northern Ireland for the first time.

The dry, sunny and warm spring means many have been hoping for a good dose of the wet stuff. Well, the weather has finally started to turn, which is good news, especially for drought-stressed crops.

In fact, the Met Office long-range forecast predicts unsettled conditions across the UK, including during the first half of June.

To put a dampener on proceedings, many plant pathogens will also welcome the moisture, including ear diseases during flowering.

For example, wet, warm and humid conditions favour the spread (rain-splashed spores), crop infection and development of fusarium species, which can cause ear blights and result in the production of harmful mycotoxins.

The farmer, merchant or processor (whoever owns the grain) has a legal obligation to make sure it is safe for human consumption and is in line with contractual and legal limits, which cover the fusarium mycotoxins in wheat grain: deoxynivalenol (DON) and zearalenone (ZON).

As there is little correlation between fusarium-damaged grains and mycotoxin occurrence, the presence of ear blight symptoms is not a good indicator of mycotoxin risk. It is why we developed the mycotoxin risk assessment.

To help demonstrate compliance with UK law, crop assurance schemes require a DON risk assessment score for wheat on the combinable crops passport.

The risk score considers:

• Region (mycotoxin levels tend to be highest in southern and eastern England)
• Previous crop (maize increases risk)
• Cultivation (more intensive cultivations disrupt pathogens)
• Varietal resistance rating* (most varieties have a fusarium ear blight rating of 6 or 7)
• T3 fungicide application (higher doses can lower risk)
• Total rainfall during flowering (GS59 to GS69)
• Total pre-harvest rainfall (GS87 to harvest)

Usually, many winter wheat crops start flowering (GS59) from the beginning of June. However, some crops have reached flowering earlier this year, due to the relatively dry conditions.

The total rainfall during flowering affects the risk assessment score (lower scores are better):

• Score 9: >80 mm
• Score 6: 40–80 mm
• Score 3: 10–40 mm
• Score 0: <10 mm

For the most reliable indication of risk, actual rainfall data for each field is best (because of the sporadic nature of showers).

However, the mycotoxin rainfall risk tool lets you look up rainfall totals at your nearest site.

Many factors influence the timing and the duration of the flowering period, such as where you farm, the season and the variety grown, which is why the tool lets you set the start and end of the flowering period to match your crop.

The tool now covers hundreds of UK-based sites, because we extended the tool to cover the main arable regions in Northern Ireland this year.

The mycotoxin risk assessment details other factors that influence the total risk score, including how an appropriate dose of an approved T3 ear fungicide (with activity against fusarium and/or mycotoxin production) can reduce risk.

*The AHDB Recommended Lists for cereals and oilseeds (RL) provides fusarium ear blight disease resistance ratings (1‒9) for winter wheat.